1. Field of the Invention
The present invention relates to a drive control apparatus for a photographic lens with a detachable lens cap to cover the front thereof, a drive control method therefor, and an imaging apparatus including the photographic lens drive control apparatus.
2. Description of the Related Art
A conventional imaging apparatus (hereinafter to be referred to as camera) is provided with a lens cap to cover the front of a photographic lens during non-use of the camera for the purpose of protection or fouling prevention of the lens. Further, along with development of thin-model, small-sized cameras, the lens barrel thereof generally incorporates the lens, and a mainstream lens barrel is of a collapsible type which moves from a non-photographable collapsed position to a photographable standby position.
There is a problem in the collapsible type lens barrel that when moved from the collapsed position to the standby position with the lens cap attached, the lens barrel front interferes with the attached lens cap to prevent the lens barrel to move, affecting the operation of photographing.
In order to prevent this problem from occurring, it is needed to detect attachment or detachment of the lens cap. For example, Japanese Laid-Open Utility Model Patent Application Publication No. Sho 60-98973 has disclosed a technique to detect the attachment or detachment of the lens cap with a switch. However, this technique has a problem that the lens cap need be of a specific shape so that the switch can be switched over according to attachment or detachment of the lens cap without fail. Another problem is that it is necessary to secure a space to dispose the switch.
Moreover, Japanese Laid-Open Patent Application Publication No. Hei 11-231374 has disclosed a technique to detect the lens cap by detecting brightness with a photometric sensor. However, this technique has a problem that in dark environment such as in night time, it is not possible to distinguish darkness due to the covering lens cap from darkness due to outside light, which may cause erroneous operation in the camera. Also, it is needed to secure a space to dispose the photometric sensor.
For another example, Japanese Laid-Open Patent Application Publication No. 2003-195393 has disclosed a lens barrel which has a built-in lens cap (optical barrier wings) configured to open responding to a manipulation to a power-on switch or the like. However, it is not always possible for the lens barrel to incorporate the lens cap depending on the structure of the photographic lens or the like.
There is still another technique to detect attachment or detachment of the lens cap by pressing the lens barrel body onto the lens cap. The problem of this technique is that when the camera is powered off with the edge of the lens barrel pressed onto the lens cap, and the lens cap is removed, the lens barrel is to be in a slightly projected state, which damages the appearance of the camera. Also, it may not be able to re-attach the lens cap on the lens barrel in the projected state.